ortac wrote:
Currently the benefits of the diesel options are just too marginal to make them attractive.
Not if AVGAS goes away 
The benefit of getting fuel vs not getting fuel is significant… I would have banned it long time ago. Polluting the environment with lead is unacceptable. There’s no justification we should be allowed to do it while everybody else isn’t.
I cannot imagine, why it is so difficult to get the big injection/Turbo/high compression-engines to burn unleaded. What’s the technical reason? Even a bigger investement is not unusual in aviation to get things adapted and there are less sensible things (e.g. ELT)….
The fuel itself prevents higher compression ratios, and there is no way around that, unless you go to – of available fuels – diesel.
One can postpone the detonation by electronic control of the engine parameters, but for various reasons we don’t have certified engine control systems in GA.
The first and only easy thing would be electronic ignition, which enables the ignition timing to be varied according to RPM, MP, CHT, etc. That is feasible today. Whether this would be enough by itself to enable a highly turbocharged engine to run on car petrol I don’t know. Obviously it would need to be carefully designed so if one of the sensors fail the thing reverts to some “safe” mode. There have been many cases where a car engine just stopped – Jaguar had a huge issue with this on the XK-something; a friend of mine would find the engine would just stop randomly on the motorway… The history of electronics in GA is unfortunately rather poor (there is an absolutely dire shortage of talent in avionics generally) which is probably why we are still flying on magnetos.
Ive often wondered at how much environmental damage is caused by such a limited amount of lead going into the air currently.
Think about it for a second. For nearly a century we were burning gasoline with lead. Millions and millions of cars. Millions of airplanes during that time frame. Leaded smog in the cities so thick you could choke on it. What happened? Yes there was respiratory disease but was it due to lead? Of course lead is not good for you. But the tiny fraction that is now being burnt is it really that much of hazard?
What about brakes with asbestos? What about the plastics which is made from oil? Its breakdown into molecular sized particles that are now entering the fisheries. If we are to wring our hands over toxic substances we should worry about those with much larger world consequences. I think focusing in on such a small target as Avfuel is comparable to the Tax office going after the mechanic for listing the cleaning of his overalls and underwear as an illegitimate expense while missing the bank exec. who stuffed a million Euros into his Swiss bank account.
Ive often wondered at how much environmental damage is caused by such a limited amount of lead going into the air currently.
Somewhere so close to zero that nobody can measure it.
The food “we” eat is a far bigger issue…
Peter wrote:
The fuel itself prevents higher compression ratios, and there is no way around that, unless you go to – of available fuels – diesel.
One can postpone the detonation by electronic control of the engine parameters, but for various reasons we don’t have certified engine control systems in GA.
That’s not correct. Apart from electronic control, a simple water injection system which was standard in the WWII supercharged designs (using much more primitive fuels) can solve the problem. Such systems were available 60 years ago and there were some for Lycontosaurus as well. The simple aero engines in use today are not “highly turbocharged”, compare it to the super- and turbocharged designs of WWII.
Peter wrote:
Obviously it would need to be carefully designed so if one of the sensors fail the thing reverts to some “safe” mode.
Largely solved by the common rail aero diesels that completely rely on the ECUs and nowadays have equal or better in flight shutdown rates. The Cabri G2 helicopter uses one electronic ignition and one traditional in its Lycoming. In a helicopter, a momentary engine stoppage means forced landing because there is no prop windmilling it (rotor decouples).
C210_Flyer wrote:
Ive often wondered at how much environmental damage is caused by such a limited amount of lead going into the air currently.
So you have the right to pollute because the others don’t? That argument doesn’t hold up. Why do you get the privilege to pollute and the owners of historic cars don’t? I for myself do not want to exercise privileges that others don’t have, that’s not what a democratic society should be about.
Peter wrote:
Somewhere so close to zero that nobody can measure it.
But if you add “so close to zero” often enough……
@ Achim
I for myself do not want to exercise privileges that others don’t have, that’s not what a democratic society should be about.
But don’t you do it aswell?
I do, because there’s no alternative. Are we talking about “principles” or about pollution? Avgas is about 0.03 percent of total fossil fuel sold in Germany. There’s about as many cars in the street i live in Munich as airplanes in all of Germany. And most of these airplanes fly 20 hours per year …
Yes, it is “pollution”, but the effects on the environment can be tolerated, for now!
Peter wrote:
The fuel itself prevents higher compression ratios, and there is no way around that,
Why is that? It seems to me that technically both G100UL and Swift would work. It seems to me it’s mostly politics and the glacially slow progress in aviation that they’re not yet approved.
C210_Flyer wrote:
by such a limited amount of lead going into the air currently
EPA says we’re now the biggest contributor to lead emissions. 363kg/year at Santa Monica SMO doesn’t sound like a small quantity to me. It also seems like lead poisoning played a certain role in the fall of the roman empire
Peter wrote:
AFAIK Lyco have not certified any turbo engines for 91UL.
I’ve had reson to check their list of approved fuel recently (Lycoming SI 1070S) and you’re right. They haven’t.
